Centrifugal pumps



Sept. 17, 1968 5 FOWLER ET AL 3,401,640

CENTRIFUGAL PUMPS Filed Dec. 5, 1966 INVENTOR 5 Baum J. FowLeR BY ARuN K BOSE was H4, w wza,

ATTORNEYS United States Patent 3,401,640 CENTRIFUGAL PUMPS Brian John Fowler and Arun Kumar Bose, Stamford,

Engiand, assignors to Newage Lyon Limited, a company of Great Britain Filed Dec. 5, 1966, Ser. No. 599,277 Ciaims priority, appiication Great Britain, Doc. 3, 1965, 51,489/65 7 Ciaims. (Cl. 103-413) ABSTRACT OF THE DISCLOSURE The invention relates to self-priming centrifugal pumps for pumping liquids, and provides such a pump with a bypass passage extending from the priming chamber into the seal chamber in which the shaft seal is mounted, and from the seal chamber into the entrainment region of the impeller within the impeller chamber, so that pumped liquid is recirculated from the priming chamber through the seal chamber for cooling purposes and from the seal chamber passes to the impeller chamber where it is reentrained by the impeller and hence serves to initiate the priming action of the pump on starting. The bypass passage between the seal chamber and the entrainment region of the impeller chamber either passes through an annular gap between the impeller hub and a surrounding wear plate fixed in the housing or, in the case of a shrouded impeller, it passes through elongated arcuate ports formed in the shroud plate near the inner ends of the impeller vanes.

This invention relates to self-priming centrifugal pumps for pumping liquids, and is concerned with improving the self-priming characteristics of such pumps by recirculation of a portion of the pumped fluid.

It is usual to provide a bypass passage for pumped liquid from the priming chamber of a self-priming pump to the eye of the impeller and so directly onto the vanes, to effect the self-priming action of the pump.

It is also known to recirculate pumped liquid from the priming chamber of a self-priming pump to the seal chamber surrounding the impeller shaft at the back of the impeller, and from there to provide a leakage path for the liquid into the volute chamber. This does not provide any asistance towards the self-priming ability of the pump, but it introduces cooling medium to the region of the seal, and thereby permits the pump to be run for long periods without any liquid passing through the pump, i.e., on what is comonly known as a snore, without liability to failure of the seal due to overheating.

According to the present invention, in a self-priming centrifugal pump for pumping liquids a bypass passage is provided for recirculating pumped liquid from the primary chamber to the entrainment region of the impeller vanes a seal chamber of the pump.

The arrangement of the invention thus provides for both cooling of the seal and enhanced self-priming of the pump by means of a single bypass passage for recirculated liquid; and moreover makes possible an improved and simplified introduction of the recirculated liquid into the entrainment region of the impeller.

In a convenient arrangement of the invention the recirculating pumped liquid passes from the seal chamber and through or past the back of the impeller into the entrainment region of the impeller vanes.

Thus in one form of the invention, in which the pump has a shrouded impeller, arcuate slots may be formed in the shroud plate of the impeller between the vanes, to act as the recirculatory ports for the passage of liquid from the seal chamber through the back of the impeller 3,401,640 Patented Sept. 17, 1968 into the entrainment region near the root of the vanes. With this arrangement it will be understood that the recirculatory ports constituted by these arcuate slots will rotate with the entrainment area of the impeller in contrast to known arrangements where the impeller vanes, and thus the entrainment area, rotate relatively to the stationary recirculatory ports through which recycled liquid is delivered to the front of the impeller.

The invention is also applicable however to pumps having open impellers, in which case a recirculatory port is formed by the provision of a sufiicient annular clearance between the periphery of the hub of the impeller and the surrounding edge of the stationary wear plate mounted behind the impeller vanes and surrounding the shaft and hub of the impeller.

The invention according to another aspect comprises a self-priming centrifugal pump for pumping liquids and having a bypass for recirculating pumped liquid, wherein the recirculated liquid is first passed through a seal chamber of the pump to act as a cooling medium for the or a rotary seal of the pump impeller in the sealing chamber, and passes thence to the entrainment region of the impeller vanes, to provide the self-priming characteristic of the pump.

The invention may be carried into practice in various ways, but two specific embodiments will now be described by way of example only with referene to the accompanying drawings in which:

FIGURE 1 is a cross-section in side elevation of a self-priming liquid centrifugal pump; and

FIGURE 2 is a front elevation of an alternative type of impeller for use in a pump of general arrangement as shown in FIGURE 1.

In the first embodiment illustrated in FIGURE 1 a self-priming liquid centrifugal pump comprises a pump casing 10 affording an intake passage 11, a volute cham ber 12 leading to an outlet (not shown), and a priming chamber 13 located above the volute chamber 12 and designed to receive a proportion of pumped liquid from the volute chamber 12, the remaining pumped liquid proceeding to the pump outlet during normal operation.

The impeller 20 of the pump is located in an impeller chamber 14 within the volute chamber 12, and is mounted on a shaft 15 journalled in a bearing casting 16 which closes the rear side of the impeller chamber and defines around the shaft 15 a seal chamber 17 in which a springloaded shaft seal 18 is housed. The impeller 20 is of open type, comprising a hub 21 mounted on the end Of the shaft 20, and a series of curved backswept vanes 40 mounted on the front face 22 of the hub 21 and radiating outwardly from it. Front and rear fixed wear plates 23 and 24 of annular form line the impeller chamber 14 in front of and behind the impeller vanes, the central aperture 25 of the front wear plate 23 constituting an inlet port through which liquid from the inlet passage 11 in the pump casing 10 passes into the eye of the impeller 20.

In accordance with the invention a single bypass passage is provided from the priming chamber 13 into the entrainment region of the impeller. This bypass passage comprises a first tube which extends through the rear wall of the pump casing 10 into the interior of the priming chamber 13, and is suitably slotted as shown at 31, and/or perforated and/or swaged within the priming chamber 13 to permit the entry of liquid into the bore of the tube 30. This first tube 30 is connected outside the pump casing to the upper end of a second tube 32, whose lower end is connected to an inlet port 33 formed in the bearing casting 16 and leading into the interior of the seal chamber 17, whereby pumped liquid from the priming chamber 13 can flow through the two tubes into the seal chamber 17. From the seal chamber 17 the bypass passage is continued past the periphery of the impeller hub 22 into the entrainment area of the impeller vanes within the impeller chamber 14. For this purpose an annular clearance 35 of appropriate radial width is formed between the impeller hub 21 and th surrounding inner edge 36 of the fixed rear Wear plate 24, for example by machining the hub 21 or the wear plate 24 of the required relative dimension. Through the annular clearance gap 35 so produced liquid will enter the entrainment region 14 of the impeller from the seal chamber 17. The entrainment region 14 will be a lowpressure region in relation to the priming chamber 13 when the pump is in rotation so that pumped liquid will tend to flow through the bypass passage from the priming chamber 13 via the seal chamber 17 into the entrainment region 14 thus cooling the seal 13 and enhancing the self-priming ability of the pump.

The annular clearance 35 between the hub 21 and the rear wear plate 24 is of frusto-conical form, being downwardly inclined from the seal chamber 17 into the impeller chamber 14 at its lower part 37, and forming a continuation of the profile of the seal chamber 17. This arrangement has particular advantage in cases where the liquid being pumped contains a proportion of sediment, as in building or civil engineering applications. If the pump lies idle for any length of time sediment settling in the seal chamber 17 will filter down into the downwardly-inclined lower part 37 of the annular gap 35. When the pump is started again, the relative rotation between the impeller 20 and the fixed rear wear plate 24 will exert a shearing action on the sediment in the annular gap 37, thus producing a self-clearing efiect which will free any blockage in the annular gap 37.

In the second embodiment illustrated in FIGURE 2 the general arrangement of the pump casing and of the impeller shaft and its seal are the same as in the embodiment already described above and illustrated in FIG- URE 1, but in this case the impeller 39 is of the shrouded type in which the vanes 40 are backed by a rear shroud plate 41 constituting a radial extension of the hub 42 of the impeller 39 to the full radius of the swept path of the vanes, the shroud plate 41 rotating as a part of the impeller 39.

In this construction arcuate slots 44 of equal radius are formed in the shroud plate 41 of the impeller 39 and extend through the complete thickness of the shroud plate 41 into the spaces between adjacent vanes, there being one such arcuate slot 44 between each pair of adjacent vanes 40. These arcuate slots 44 which are concentric with one another and with the impeller axis constitute the recirculatory ports by which liquid from the seal chamber 17 passes through into the entrainment region 14 of the impeller 39, and it will be appreciated that this construction has the advantage that the slots themselves rotate with the entrainment region 14, thereby reducin turbulence in the impeller.

We claim:

1. A self-priming centrifugal pump for pumping liquids, which comprises a pump housing, an impeller chamber formed in the housing, a rotary centrifugal impeller mounted in the housing on a rotary shaft extending into the housing, the impeller having spaced vanes whose inner ends lie on a common inner circumference of the impeller and whose outer ends lie on a common outer circumference of the impeller, and the impeller chamber having a low-pressure entrainment region traversed by the inner ends of the vanes and a high-pressure discharge region radially outside the outer ends of the vanes, a priming chamber in the housing communicating with the impeller chamber to receive and hold a supply of pumped liquid from the discharge region for priming the pump, a seal chamber in the housing through which the shaft extends, and seals in the seal chamber for sealing the shaft to the chamber, and a bypass passage extending from the priming chamber into the seal chamber into the entrainment region of the impeller chamber through which bypass passage pumped liquid from the priming chamber is recirculated through the seal chamber to the entrainment region.

2. A pump as claimed in claim 1 whose impeller is of open type having a hub from which the vanes extend outwardly, and whose housing includes a part fitting closely around the periphery of the hub and adjacent to the edges of the vanes on the side of the impeller nearest to the seal chamber, and in which a clearance is provided between the periphery of the hub and the housing part, said clearance constituting a part of the bypass passage ex tending from the seal chamber into the entrainment regron.

3. A pump as claimed in claim 2 in which said housing part comprises a flat wear plate of annular form fixedly mounted in the housing adjacent to the impeller vanes and surrounding the impeller hub and shaft, and in which said clearance is constituted by an annular gap formed between the hub and the inner periphery of the surrounding wear plate.

4. A pump as claimed in claim 1 whose impeller is of shrouded type having a hub from which the vanes extend generally radially, and a shroud plate secured to said hub and extending radially outwardly therefrom one the side of the impeller facing towards the seal chamher, the shroud plate being in connection with the adjacent longitudinal edges of the vanes, and in which ports are formed in the shroud plate adjacent to the inner ends of the vanes, said ports constituting part of the bypass passage through which the recirculated liquid passes from the seal chamber through the shroud plate into the entrainment region.

5. A self-priming centrifugal pump as claimed in claim 3 in which the annular gap between the hub and the wear plate is of frusto-conical form diverging away from the seal chamber, and in which the bottom wall of the seal chamber is downwardly inclined towards the annular clearance.

6. A self-priming centrifugal pump as claimed in claim 5 in which the seal chamber is of frusto-conical form and the outer surface of the annular gap comprises a coaxial extension of the surface of the seal chamber at the larger end thereof.

7. A self-priming centrifugal pump as claimed 1n claim 4 wherein the ports in the rear shroud plate comprise arcuate slots formed in the shroud plate between the vanes, the slots all being concentric with one another and with the impeller shaft.

References Cited UNITED STATES PATENTS 1,946,212 2/1934 Jacobsen 103-113 3,070,028 12/1962 Loy et a1. 103111 3,128,713 4/1964 Nechine 103-111 879,484 2/ 1908 Morterud 103103 1,871,662 8/1932 Carrier 103111 2,741,991 4/1956 Disbrow 103111 2,900,919 8/1959 Anderson et a1. 103111 FOREIGN PATENTS 877,878 9/1961 Great Britain.

HENRY F. RADUAZO, Primary Examiner. 

